1. Field of the Invention
The present disclosure is directed to a backlight unit assembly, a liquid crystal display having the same, and a dimming method thereof, and more particularly to a backlight unit assembly, a liquid crystal display having the same, and a dimming method thereof, which can minimize image distortion by setting a plurality of lookup tables having different pulse width data in accordance with grayscale classes and performing dimming by using different lookup tables in accordance with the grayscale classes of an image signal for each frame of an image.
2. Description of the Prior Art
Flat panel displays, such as liquid crystal displays (LCD), plasma display panels (PDP), or the like, have been replacing cathode ray tubes (CRT) in computer display monitors. However, since the liquid crystal display is not a self-illuminating device, separate light sources are required. Accordingly, the liquid crystal display is provided with a backlight unit installed in a lower part of a liquid crystal display panel, which displays an image using light emitted from the backlight unit. A light emitting diode (LED) has recently been spotlighted as a light source of such a backlight unit.
A backlight unit using light emitting diodes as light sources can perform local dimming to improve contrast ratio and reduce power consumption. Generally, the local dimming is performed such that a grayscale average of the image data of pixels corresponding to one block of a liquid crystal display panel is calculated, and an adjusted power is applied to a light emitting diode block corresponding to the one block of the liquid crystal display panel to obtain a luminance corresponding to the calculated grayscale average.
Here, pulse widths for obtaining the luminance corresponding to the respective grayscales are measured in advance and stored in a memory in the form of lookup tables. For each frame of an image, the pulse widths are adjusted with reference to the lookup tables, and then the adjusted pulse signal is applied to the backlight unit to adjust the luminance. Generally, the lookup table is set by setting the grayscale values of the pixels of the whole liquid crystal display panel to the range 0˜255, adjusting the pulse widths where the luminance is adjusted corresponding to the grayscale values, and then providing corresponding pulse width data.
As described above, according to a conventional liquid crystal display, the local dimming is performed using one fixed lookup table. For local dimming with reference to the lookup tables set as above, light leakage of liquid crystals can be effectively prevented in a dark part of the image.
However, in performing local dimming using one lookup table, if the image is dark on the whole, and only a part thereof is bright, the light intensity of the bright part can cause image distortion. Specifically, when an image, which is bright on the whole but which has specified blocks that are relatively dark, is displayed, the luminance of the specified dark blocks is affected by neighboring bright blocks. However, in the case of displaying an image, which is dark on the whole, but which has specified blocks that are relatively bright, the luminance of the specified bright blocks is not affected by the neighboring dark blocks, and thus their luminance may be reduced.